This invention relates generally to printers, and more particularly, although not exclusively, to improving the image quality of a print job.
It is generally known that inkjet printers utilize at least one printhead possessing a plurality of nozzles through which ink drops are fired onto a medium, e.g., fabric, paper, vinyl etc., to create an image on the medium, e.g., plot, drawing, etc. According to one type of inkjet printer, ink is typically supplied substantially continuously over a plurality of resistors generally located beneath the openings of the nozzles. In use, certain of the resistors are activated, i.e., heated, to vaporize a portion of the ink on the resistors, thereby causing a portion of the ink to be fired through the respective nozzle openings. According to another type of inkjet printer, ink is typically supplied substantially continuously over a plurality of piezoelectric elements located beneath the openings of the nozzles. In this type of printer, certain of the piezoelectric elements are caused to deform at a relatively rapid rate, thereby causing ink positioned thereover to be fired through the respective nozzle openings to produce pixels.
To create an image on the print medium, the printer typically controls the nozzles to produce a pattern of pixels corresponding to the image. The nozzles are generally arranged on one or more printheads that travel back and forth across the surface of the print medium. In this regard, FIG. 1 illustrates a conventional large format inkjet printer 110 having a pair of legs 114, left and right sides 116, 118, and a cover 122. The printer 110 includes a carriage 100 supporting a plurality of printheads 102-108. The carriage 100 is coupled to a slide rod 124 with a coupling 125. As is generally known to those of ordinary skill in the art, during a printing operation, the carriage 100 travels along the slide rod 124 generally in a Y-axis direction 103 to make a printing pass, typically from the right side 118 to the left side 116 of the printer 110. In addition, as the carriage 100 travels along the Y-axis 103, certain of the printheads 102-108 drop or fire ink onto a medium 130 through a plurality of nozzles (not shown).
Typically, the medium 130 travels in an X-axis direction 101 at certain times during the printing operation. By virtue of performing a plurality of printing passes over the medium 130 by the carriage 100 in the above-described manner, an image, e.g., plot, text, and the like, may be printed onto the medium.
Also illustrated in FIG. 1 is a printer control panel 120 located on a right side 118 of the large format inkjet printer 110. The printer control panel 120 typically functions as an interface between a user and the printer 110 to enable certain printer operations to be set (e.g., medium advance, printmode, etc.). In addition to housing the printer control panel 120, the right side 118 of the printer 110 typically also houses printer components for performing printing operations (e.g., printer electronics, a service station for servicing operations on the printheads 102-108, etc.).
In performing printing operations with inkjet printers, it is generally known that the print quality and the throughput, i.e., amount of time required to print a plot, may be inversely related. That is, to increase throughput, the print quality is oftentimes sacrificed, or vice versa. To maintain a preferred level of print quality, servicing operations are typically performed on the printheads 102-108. In this respect, although not shown in FIG. 1, inkjet printers typically possess a service station located (xe2x80x9cspittoonxe2x80x9d) to perform the above-described servicing operations on the printheads 102-108.
There are generally two ways in which the nozzles of the printheads 102-108 may be xe2x80x9crefreshedxe2x80x9d, i.e., cleaned. The nozzles may be refreshed by firing ink drops onto the medium 130, i.e., printing, or by spitting ink drops into the spittoon. Thus, those nozzles of the printheads 102-108 that actively drop ink onto the medium typically are not required to spit into the spittoon during various printing passes.
If it is preferred to increase throughput, the number of servicing operations performed on the printheads 102-108 may be reduced. In this respect, the length of time between the servicing operations may also be increased. One problem associated with increasing the length of time between servicing operations is that the properties of fired ink drops may deteriorate, thereby compromising the print quality. For example, ink in position to be fired from the nozzle may become dried and thus not fired through the nozzle. This effect is generally referred to as xe2x80x9cdecapxe2x80x9d and typically occurs when a maximum amount of time a nozzle may be idle (i.e., not firing or spitting ink drops) before an ink drop may be ejected from that nozzle is exceeded. In addition, xe2x80x9cslewing decapxe2x80x9d generally refers to the maximum amount of time a nozzle may be idle during a pass across a medium. Moreover, because the nozzles are moving, the effects of xe2x80x9cslewing decapxe2x80x9d on the nozzles are typically worse than xe2x80x9cdecapxe2x80x9d. As a consequence, slewing decap times are generally shorter than decap times.
To reduce the negative effects of decap, the spittoon typically performs servicing operations on the printheads as well as capping the nozzles when the printheads are idle for a certain period of time. For example, the printheads typically spit ink into the spittoon at various times during a printing operation to substantially prevent the occurrence of decap. Additionally, the spittoon may also include a mechanism for wiping the nozzles of the printheads at various times to generally attempt to wipe off ink dried in the nozzles. Although the performance of the above-stated servicing operations on the printheads has been found to relatively increase the life of the printheads as well as the quality of the printed image, one disadvantage of performing a relatively large number of servicing operations is that the throughput may become compromised.
A typical workflow utilized by the large format (i.e., 40 inches or more) inkjet (e.g., thermal, piezoelectric cell, etc.) printing industry follows. A print job is initiated. For example, a poster, is sent to the printer. Some startup time may pass (e.g., a few seconds or so) as the job is being processed through the pipeline and the printer is getting ready to print the job. During the startup time, the printer typically takes this opportunity to perform actions that may result in lowering the rate of defects. For example, the servicing protocols mentioned above. In addition, the printer may have performed servicing at startup i.e., when the printer was turned on. To continue, the job is printed as described above. The job length is defined typically by the length of the file, for example the size of the poster. Once the job has finished printing, the print medium is typically cut and the printer may perform one or more servicing actions prior to the next job. This particular series of events (i.e., workflow) is generally utilized by the large format inkjet printing industry.
In the textile printing industry, however, a number of differences may be noted. For instance, the print medium is relatively larger. In this regard, fabric mills typically produce fabric five meters wide and several hundred meters long. Each of two sides or edges of the fabric are termed xe2x80x9cselvagexe2x80x9d. Typically, the selvage is woven differently to reduce tearing and fraying of the material. The fabric is generally rolled to facilitate transport and handling. The roll is then transported to a textile printing mill.
A typical workflow utilized by the textile printing industry follows. The textile mill receives the roll and load it into a processing machine. Typically the machine unrolls the fabric, washes and bleaches the fabric. As processing continues, a tensioner is utilized to remove wrinkles. The tensioner grasps each selvage edge of the fabric and stretches the fabric to remove any wrinkles i.e., a form of ironing. The fabric may be processed through a series of presses to further reduce wrinkles and relieve mechanical stress of the fabric.
Rotary silkscreen printing presses are typically utilize by the textile industry. In a relatively fast (e.g., thousands of meters per hour) and substantially continuous process, the fabric is glued to a belt, printed, removed from the belt, cleaned, and rolled or cut and stacked. The belt is generally a perforated rubber mat, about three meters wide and about thirty meters long. The belt is heated and dried. A glue is spread over the belt and the fabric is pressed on the belt. Heat is applied to set the glue. At this point, the fabric is generally ready for printing.
Rotary silkscreen tubes are placed on the fabric. The surface of tubes have been processed to form an image. The image on the surface of the tube is permeable to ink. Ink is sprayed in the tubes and a magnetic knife within the tube acts as a xe2x80x9csqueegeexe2x80x9d to spread the ink over the inside of the tube. The tubes roll as the fabric moves underneath and the image is transferred to the fabric. The fabric is pulled off the belt at an angle. Relatively high-pressure water nozzles underneath the fabric are utilized to remove the glue from the fabric and the glue covered surface of the belt is cleaned as it travels back to have more fabric attached.
Typically, every color is mixed. For example, when printing a light blue, a light blue ink may be mixed and sprayed in the rotary silkscreen tube. In addition, another form of color mixing such as spot color (i.e., producing a final color by mixing more than one color directly on the fabric) may also be utilized. However, process imaging, as is performed in the inkjet industry is generally not performed. Furthermore, rotary silkscreen printing presses may utilize twenty or more color stations whereas inkjet printing generally utilizes eight or fewer colors.
In the textile printing industry, the defect rate is relatively important. For example, relatively high-end print medium (e.g., silk, linen, wool, etc.) may cost more than one hundred dollars for each meter length. The cost of the inks used in textile printing is relatively expensive as well. A significant defect may effectively ruin as much as ten meters of material. Thus, conventional rotary silkscreen printing has developed into a relatively robust printing system. Typical defect rates are approximately four defects per six hundred meters. A convention inkjet printer may have a defect rate of ten to fifty times the defect rate of a conventional rotary silkscreen printing press. However, the cost for a typical rotary silkscreen press may exceed five million dollars compared to a few thousand dollars for an inkjet printer.
In one respect, the invention pertains to a method for improving the image quality of a print job. In the method, a print job having a print length and a print width is initiated. The print job is paused in response to at least one of the print length and the print width exceeding a modifiable servicing interval. A service strip is printed and evaluated to determine whether the image quality of the print job is above a predetermined quality threshold. The print job is resumed in response to the print job being above the predetermined quality threshold.
In another respect, the invention pertains to a system for improving the image quality of a print job. In the system, a printer is controlled by a processor to initiate the print job having a print length and a print width. In response to at least one of the print length and the print width exceeding a modifiable servicing interval, the printer is controlled by the processor to pause the print job and print a service strip on a print medium. The service strip is sensed by a sensor system and data associated with the sensing of the service strip is relayed to the processor. The data associated with the sensing of the service strip is utilized by the processor to evaluate the service strip and determine whether the image quality of the print job is above a predetermined quality threshold. In response to the print job being above the predetermined quality threshold, the printer is controlled by the processor to resume the print job.
In yet another respect, the invention pertains to an apparatus. The apparatus includes a printhead configured to print on a print medium and a controller configured to control the printhead to print a print job having a print length and a print width on the print medium. The controller is further configured to control the printhead to pause the print job and print a service strip on the print medium in response to at least one of the print length and the print width exceeding a modifiable servicing interval. The apparatus further includes a sensor configured to sense the service strip and relay data associated with the sensing of the service strip to the controller. In this regard, the controller is further configured to evaluate the service strip based on the data associated with the sensing of the service strip and determine whether the image quality of the print job is above a predetermined quality threshold based on the evaluation of the service strip. In response to the print job being above the predetermined quality threshold, the controller is further configured to control the printhead to resume the print job.
In comparison to known prior art, certain embodiments of the invention are capable of achieving certain aspects, including some or all of the following: (1) saves user""s time; (2) improves printer servicing protocol; and (3) reduces printer error rate. Those skilled in the art will appreciate these and other aspects of various embodiments of the invention upon reading the following detailed description of a preferred embodiment with reference to the below-listed drawings.